Astronomers have found what they describe as the strongest evidence yet of possible life beyond the solar system, following the detection of key chemical signatures in the atmosphere of a distant exoplanet.
A team led by Professor Nikku Madhusudhan at the University of Cambridge used the James Webb Space Telescope to identify dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) in the atmosphere of K2-18 b, a planet 124 light years from Earth. Both compounds on Earth are almost exclusively associated with biological processes, particularly marine life.
“This is the strongest evidence to date for biological activity beyond the solar system,” said Madhusudhan, while cautioning that the findings are not definitive proof of life. “We have to question ourselves both on whether the signal is real and what it means.”
The presence of DMS and DMDS was observed with a statistical confidence level of “three-sigma”, indicating a 0.3% probability that the results are due to chance – strong, but below the gold standard in physics.
K2-18 b, orbiting within the habitable zone of a red dwarf star in the Leo constellation, has long been considered a candidate for habitability.
The planet is 2.6 times larger than Earth and nine times more massive. Scientists previously believed it could harbour a deep ocean.
Follow-up observations now suggest the atmospheric conditions may be suitable for life, though the exact nature of the planet remains debated. Some experts suggest K2-18 b could instead be a gas planet or one with magma oceans.
Dr Nora Hänni from the University of Berne noted that DMS was also detected on a lifeless comet, urging caution. “We would have to strictly rule out all other options before claiming life,” she said.
Still, the results mark a major step forward in exoplanet research. “It’s mind-boggling that this is possible,” said Madhusudhan. “Decades from now, we may look back at this moment as the point when the living universe came within reach.”
The findings have been published in The Astrophysical Journal Letters.
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